<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .wai{
      margin: auto;
      padding-top: 50px;
      padding-left: 100px;
      background-color: pink;
      height: 500px;
      width: 500px;
    }
    .in{
      margin: auto;
      padding: 30px;
      background-color: blue;
      height: 300px;
      width: 300px;
    }
  </style>
</head>
<body>
  <div class="wai">
    <!-- 标准盒子模型和IE盒子模型 通过<!DOCTYPE html>来识别采用标准盒子模型-->
  <div class="in">
    <span>我是span的标签</span>
  </div>
</div>
</body>
</html>